Saddam Hussein appeared poised last night to agree to resumed UN arms inspections in Iraq, in a deft move that looks likely to complicate Washington's resolve to unseat him.

At crucial talks in Vienna with the chiefs of the UN inspection mission, senior Iraqi officials for the first time discussed the nitty-gritty of an inspection regime abandoned almost four years ago and pledged to supply four years of detailed reports on Iraq's dual-use technology which can be deployed for military purposes.

"They are being positive, businesslike and they're coming with a desire to reach an agreement," Mohammad El Baradei, the head of the UN's nuclear watchdog, said of the Iraqi team.

Mr El Baradei, the Egyptian head of the International Atomic Energy Agency which is preparing to send nuclear arms investigators to Iraq with other UN sleuths hunting evidence of President Saddam's chemical, biological, and ballistic missile arsenals. The UN hopes to have teams of inspectors in Iraq in three weeks.

A senior source involved in the talks said: "Unless the UN security council tells us not to go, we probably will go. The Iraqis are now saying come.

Hans Blix, the Swedish diplomat who heads the inspectors, said: "Everything was discussed. It was the first reading of all the practical arrangements... There were many specific clarifications."

But while UN officials were optimistic about returning to Baghdad to enjoy "unfettered access", Donald Rumsfeld, the US defence secretary, described any Iraqi pledges on inspections as "patently false".

With the Vienna talks nearing a breakthrough, and with war apparently hinging on the inspection regime and President Saddam's treatment of it, the big question was how the US would respond and whether it could push through a new UN resolution mandating armed force against Iraq.

The US, backed by Britain, is meeting strong resistance from Russia and France. Senior UN officials in Vienna were also critical of some aspects of the US plans. They said there was no point in international troops escorting inspectors, as suggested by Washington.

Although the issue of the new UN resolution overshadowed events in Vienna and may have focused Iraqi minds, it did not feature in the talks, said UN diplomats.

But other sources said both sides were acutely aware of the "dramatic impact" that the US draft resolution could have. "All sides are intensely aware that things are happening elsewhere," said one official.

Yesterday's talks focused on the terms for inspections, highly technical conditions governing issues such as logistics, security, accommodation, use of equipment, access to sites and overflight rights for UN helicopters and aircraft.

It was the first time such detailed talks had taken place since inspectors left Baghdad in 1998 ending almost eight years of scrutiny. And UN diplomats were sanguine last night that Iraq would bend.

One big issue not on the Vienna agenda, however, was Iraq's eight presidential palaces replete with estates and facilities that have always been kept closed to inspectors.

"That's an issue we're not discussing. That's for the security council," said the senior source.

And while the rulebook for inspections would be rewritten if a tough new American UN resolution prevails, officials insisted this would not change their mandate, merely "refine" it. "The basic mandate will not change," said the senior source. "We are there for the long haul."

Once back inside, inspectors would need a year to establish what changes, if any, have been made to Iraq's military build-ups, the source added.